The present invention addresses itself to the field of components for planetary type automatic transmissions typically used in automotive vehicles, and making use of planetary gear sets controlled by friction elements such as hydraulic clutches and brakes.
For a long period automatic transmissions used in automotive vehicles have had only three speeds, then they offered four, and in the last few years a tendency has been observed to go to five speeds in order to satisfy a customer need which first appeared in the top end of the market and is now extending to medium size vehicles. Some manufacturers are now even looking at offering six speed automatic transmissions.
In an effort to meet that need, manufacturers have generally designed transmissions which use several clutches located directly on the transmission input shaft or clutches positioned in such a way that they drive several transmission members at input speed.
In order to optimize these transmissions, it has been proposed, for instance in document EP-A-0 434 525, to drive two transmission members not at input speed but at a reduced speed.
The present invention proposes to reduce the bulk of these transmissions particularly in the axial direction.
The object of this invention is an integrated assembly comprising a hydraulic clutch and a speed reducing planetary gear set, said assembly including, on one hand, a stationary oil supply bush, a rotating casing integral with an oil supply sleeve receiving at least one piston, a partition called end partition, and at least one set of friction discs so as to drive at least one friction hub, and, on the other hand, a speed reducing planetary gear set including a ring gear to be driven by an input shaft, a stationary sun gear and a planet pinion carrier, characterized by the fact that the end partition is fixed for rotation with the oil supply sleeve and with the casing, and that it is driven directly by the planet pinion carrier.
Preferably the planet pinion carrier is assembled directly on the end partition and the sun gear is held stationary in rotation directly by the stationary oil supply bush.
Advantageously the planet pinions rotate on shafts which have extensions fitted in bores machined in the end partition and contributing in transmitting torque between the planet pinion carrier, the end partition, the oil supply sleeve and the rotating casing.
Preferably the end partition and the piston define a centrifugal pressure compensation chamber between themselves.
Advantageously the shafts of the planet pinions are crossed by longitudinal channels for the lubrication of the planetary gear set which are parallel to the shafts and open in the centrifugal compensation chamber.
Preferably the lubrication channels provided for in the shafts of the planet pinions ensure the lubrication of the planetary gear set as well as the supply of oil to the compensation chamber.
Advantageously the centrifugal compensation chamber is supplied with oil coming through channels provided for in the stationary oil supply bush and in the oil supply sleeve.
Advantageously the oil supply channels provided for in the stationary oil supply bush and in the oil supply sleeve provide oil to the compensation chamber as well as lubrication for the planetary gear set.
Preferably the end partition is also fixed for translation with the rotating casing; the end partition consists of three elements i.e. a first element in the shape of a hub having splines engaged in corresponding splines of the oil supply sleeve, a second element in the shape of a nut having a threaded part engaged in a corresponding thread of the oil supply sleeve, and a third element in the shape of a piston having an oil-tight seal and engaged in the piston the first and second elements of the end partition are assembled by screws.
Advantageously, two axial bearings are mounted, one between the sun gear and the planet pinion carrier, the other between the planet pinion carrier and the ring gear so as to ensure simultaneously the necessary clearances between the sun gear, the planet pinion carrier and the ring gear and the axial position of the whole assembly; an intermediate spacer is set between the stationary oil supply bush and the sun gear and is used to adjust the axial position of the whole assembly.
The object of the present invention is also an automatic transmission, more particularly for vehicles, including an integrated assembly such as the one described above.